@EnvironmentObject

declare an environment object

SwiftUI ⟩ Data Flow ⟩ @EnvironmentObject

The @EnvironmentObject property wrapper is used to declare (in a subview) an environment object property provided by an ancester view.

// app
struct MyApp: App {
    
    // ⭐️ 1. initialize a state object (as the app's model data)
    @StateObject private var modelData = ModelData() 
    
    var body: some Scene {
        WindowGroup {
            RootView()
                // ⭐️ 2. put the model object in the environment.
                .environmentObject(modelData)         
        }
    }
}

// assume Subview is a subview of RootView in the view hierarchy
struct Subview: View {

    // ⭐️ 3. get the model object from environment.
    @EnvironmentObject var modelData: ModelData      
    
    var body: some View { ... }
}

Be sure to set a corresponding model instance on an ancester view by calling its .environmentObject(_:) modifier.

👥 相關

• Use ObservableObject to declare an observable object type.
• Use @Published to declare published values in an observable object type.
• Use @StateObject to initialize an observable object.
• Use .environmentObject(_:) to put the model object in the environment.
• Use @EnvironmentObject to declare an observable object property provided by an ancestor view.
• observer： any view or object that uses the observable object's data.
• data model：data shared with any views in your app.

📘 手冊

• SwiftUI ⟩ Model data ⟩

  • EnvironmentObject
  • .environmentObject(_:)
• Combine ⟩ ObservableObject (protocol)
• SwiftUI ⟩ Model data ⟩ @ObservedObject (property wrapper)

📗 參考

• Majid ⟩ The difference between @StateObject, @EnvironmentObject, and @ObservedObject in SwiftUI #todo